Organic food sales have increased exponentially over the past decade, largely due to consumer perceptions of improved nutritional quality and taste. However, as I’ve explained before, there is scant scientific evidence that growing food organically improves its quality on either front. Since people have a wide array of intellectual biases, some scientists have decided to ask more balanced judges to weigh in on the issue: birds.

It turns out birds aren’t bird brains when it comes to what they eat. A number of species of birds have been shown to choose foods that contain higher levels of healthy things like protein and antioxidants and lower levels of not-so-healthy things like heavy metals and pesticides. Since they’re such finicky eaters, scientists figured to let them choose between conventionally and organically grown food, and see which they deemed better for them. The vote was unanimous: birds prefer non-organic.

Birds Think Conventional Food Is Better

Researchers from Newcastle University purchased Alchemy variety wheat from a number of organic and conventional producers in Europe. They then ground the seed into 2mm or smaller sizes so that there was no textural difference between the two types. In their first experiment, they provided caged canaries with both types of wheat in identical bowls, and recorded how many seeds of each type they ate in 20 minutes. 66% of the time, they picked the non-organic variety – and they picked it more often as time went on, suggesting that those that tried both decided the conventional was better and stopped choosing the organic.

But maybe, the scientists thought, that since canaries are domesticated, it’s possible their food preferences are skewed by what’s provided in their normal, canary feed. Instead, they decided, they wanted to see what wild birds thought of organic and conventional wheat varieties.

They placed each variety in a bird feeders and put them in different gardens throughout northeast England. They measured the weight of food taken from each tube every two days for six weeks. Since wheat isn’t commonly used in commercial food for garden birds, it’s much less likely that they’d have a preference for either type based on previous encounters. To make sure that their own biases didn’t get involved, they coded the bags of wheat and didn’t tell the people who filled the feeders which was which, so they had no idea which feeder contained which type until after the experiment was finished. They chose a few different farms for each type, to make sure that it wasn’t just the effect of one farm’s practices. And just in case position mattered, they swapped the positions of the feeders on the farms, too, halfway through the experiment.

The garden birds, like the canaries, preferred the non-organic food. At 39 of the 45 gardens tested, conventional food eaten outweighed organic food eaten. On average, conventionally grown wheat accounted for ~60% of what the birds ate. And again, the scientists found that as the experiment went on, the birds ate less and less organic wheat.

Why Did The Birds Prefer Conventional Wheat?

The big question, of course, is why did the birds prefer the non-organic varieties? The researchers made sure that texture, size, and position weren’t factors. So what about the conventional wheat was so appealing?

To try and get to the bottom of that question, the scientists tested the different varieties of wheat. They tested their physical properties (weight per thousand seeds, hardness), nutritional levels (moisture, protein, fat, carbohydrate, energy, amino acids), and levels of potential negative qualities (toxin burden, microbes, oxalic acid, and pesticide residues). Levels of moisture, fat, carbohydrate, pesticide residues, cadmium, lead, microbial contamination (Escherichia coli, Salmonella spp., Enterobacteriaceae), oxalic acid, hardness and amino acid content were not significantly different between samples.

They did find one thing that was different, though: levels of protein. The conventional wheat they gave the canaries was 26% higher in protein than the organic, and the wheat they gave the garden birds was 6-26% higher (depending on which farm the conventional or organic wheat came from).

Could protein explain the difference in preference? Well, they decided to test that, too. They grew new samples of wheat under four different levels of fertilizer, yielding four types of wheat that were identical in every way except how much protein they contained. They then took the lowest protein variety and the highest protein variety (a difference of 14% between them) and asked canaries for their opinion. The bird’s choice? The higher protein food.

Ecologically, it makes perfect sense. Protein is an essential nutrient in the diet of all birds and mammals and is often limiting – especially for species that eat grains, which aren’t high in protein to begin with. Studies have found that birds and mammals, particularly if stressed, pick higher protein options. So when the birds in this study were presented with, as far as the birds (and the experimenters!) could tell are two equal foods except that one has more protein, why wouldn’t they choose the higher protein option?

So What Does This Mean For Non-Birds?

While this study is fascinating, and may speak to potential ecological implications of organic farming, it doesn’t say much about whether we should buy organic food or not. Just because the birds chose the conventionally grown wheat doesn’t mean we should, too.

The study found a clear nutritional distinction between the wheat types they used. In a grocery store, things get much more complicated. What would have happened if the conventional wheat had higher protein levels but also had higher pesticides? Would the birds have weighed the risk and reward? It’s anyone’s guess. Also, studies have gone back and forth about whether there are or aren’t differences in nutrition between organic and conventional foods. Even if we were to say we should eat whichever has higher X or lower Y, the jury is still out on organic v. conventional in that respect, too. Furthermore, it’s hard to compare bird nutrition to human nutrition, even though birds tend to prefer foods that are healthy for us, too.

Of course, we can learn a lesson from our feathered friends – they consistently choose the healthiest food option available. How many of us can say the same?

McKenzie, A., & Whittingham, M. (2010). Birds select conventional over organic wheat when given free choice Journal of the Science of Food and Agriculture DOI: 10.1002/jsfa.4025